Lycoming O-360 LOP or ROP?

jd21476

jd21476

Line Up and Wait
Joined
Jan 17, 2018
Messages
702
Location
San Diego, CA
Display Name
Display name:
jd21476
I have a Piper Comanche 180 with the O-360 and I just installed a JPI EDM 730 with FF. I have been reading up a lot on LOP or ROP but I cant find which is best for my engine. Some of the things I have read said flying LOP can hurt some engines and others have said it is optimal. Where can I find info on which is best for this engine?
 
well you just opened a can of worms.. so sit back and enjoy the ride.

same engine - here is what i do.

below 60% power - lean as much as you want, you are not going to hurt the engine. last night i flew 1.4 hrs burning about 6.4 gal/hr at 56% power. CHTs in 350 or below, EGT at 1550 range (LOP) based on my engine, your number may be diff and dont get too hung up on the EGT absolute number. anything at or above 65% i use 100 ROP. in a carbe-ed engine good luck getting a good LOP setting. some people recommend opening the carb heat knob a little for even fuel burn, i havent tested it or use it.
 
I fly the same engine in the Archer. It’s carbureted so LOP operations aren’t really in the playing field. 50F ROP seems to be a fine power setting for most operations.
 
GeorgeC said:
It's carbureted, so LOP is pretty much out. Keep your CHTs <380, lean until rough, enrich until smooth, fuggedaboutit.
Click to expand...

In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.

Bob Gardner
 
With carb-ed engines it is just a matter which the cylinders do you want to replace first, LOP the richest will fail first. simply because the leanest will be cooler and cleaner.
When you run in the red box, cylinders will fail.
 
bobmrg said:
In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.
Click to expand...
I would like to read that article, Bob.

I see an article from Mike Busch on the June 2020 AOPA Pilot magazine titled "Justice Denied?", but I cannot find anything related to CHTs or sticking valves in there. Can you please say what the article was called, and which month of the magazine?

Thanks,
Martin
 
bobmrg said:
In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.

Bob Gardner
Click to expand...

That is course reversal of what he has said before. May be new data points?
 
bobmrg said:
In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.

Bob Gardner
Click to expand...
While difficult to get LOP in my Archer, I can do it when flying lower than 65%. However, I don’t bother anymore and pretty much fly 65% on all my cross countries at peak EGT to max range with stingy fuel burn. The CHT runs about 350+ in cyl 3 and others lower but above 310-320. That’s the best I can do regarding CHTs unless I constantly run higher power settings. So I will probably never sniff 380 and above unless I’m stay at Vy( which I don’t do since I lower the nose for a climb at 80-85 kts to keep the CHTs lower) in the climb during warm days before getting up to cruise altitude and getting to my preferred lean.
 
Last edited:
WannFly said:
That is course reversal of what he has said before. May be new data points?
Click to expand...
I really want to see how Mike worded that. "Low power" and "high CHTs" usually don't coincide. In my airplane, I cannot get to 380 degrees at low power.

- Martin
 
The highest I can get my CHTs (IO-360) at 65% power is about 330 in level flight. If I’m leaned to 25 LOP my hottest cylinder hardly goes above 300.
 
bobmrg said:
In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.

Bob Gardner
Click to expand...

I'd like to see that as well. Everything I've ever read or heard MIke Bush say on the topic has always been focused on keeping the CHTs cool, as it's high CHTs that damage engines. Running LOP, when possible, results in less power, almost always results in lower CHTs and less engine stress.

-----

Mike Bush is also adamant about staying out of the "Red Box" or "Red Fin". Areas in the Red Box or Red Fin almost always involve CHTs over 400 degrees F, regardless of whether you are ROP or LOP

The Red Box isn't constant in size, as it gets smaller as power settings are decreased until at around 60%-65% power it disappears entirely. Depicting it requires a chart for each power setting and the box gets smaller as power settings are reduced.

The Red Fin takes different power settings into account by reflecting percent power on one axis. For example at 85% power you may need to be at least 75 degrees LOP, or 225 degrees ROP to stay out of the fin. At 75% the minimum numbers may decrease to 40 degrees LOP or 175 degrees ROP. At 65% it may be further reduced 10 degrees LOP or 80 degrees ROP.

At 60% or less there usually isn't any mixture setting that'll hurt the engine, and 75% ROP is usually best power, with best economy being slightly LOP.

When going from ROP in climb to LP in cruise Mike Bush recommends a "big pull" in 2-3 second to get to the lean side of peak on the lean side of the fin. If you've got fuel flow, you can use that to get in the ballpark before using the lean fine. if not, you can pull until it runs rough or loses significant power, enrich slightly and then start the "Lean L" process.

Mike has also indicated that when we wants to go fast (high power settings) he leans so that the hottest running cylinder (3 or 4 in a four cylinder Lycoming) does not exceed a pre set target: 400 degrees F for a Lycoming; 380 degrees F for Continentals; and 20 degrees cooler in aircraft with very efficient cooling systems. He then recommends enriching the mixture slightly if running ROP and temps creep up, or leaning a bit more if running LOP and the temps creep up. Basically he's using those CHTs to stay out of the Red Box/Red Fin. That said, he also recommends cruising LOP since it's more fuel efficient and usually results in cooler temperatures.

-----

You'll have to see if you can operate LOP with your engine.

I have mixed results and whether LOP works or not with my fuel injected Lycoming depends on altitude, OAT, power setting, and probably phase of the moon. Adding a bit of induction/carb heat can sometimes let you operate LOP without roughness.

When I can't run 15-25 degrees or so LOP at 55-65% power, I usually run 50 to 100 degrees ROP. At higher settings that would be bad, but at those low power settings it's outside the Red Fin. CHTs stay around down 360-370 degrees on a 90 degree day, so I'm not cooking the engine. I'm also not fouling plugs. When I can run 15-25 degrees LOP, the CHTs are down around 350 degrees F on a similar day.
 
Martin Pauly said:
I really want to see how Mike worded that. "Low power" and "high CHTs" usually don't coincide. In my airplane, I cannot get to 380 degrees at low power.

- Martin
Click to expand...

Yah last evening I was trying out the LOP based on your video, at 60% power I couldn’t get the CHTs above 350, I was at 3500 with 14C OAT.
 
I do the big pull as well. On my engine, if I pull the mixture to where the lower lip of the mixture arm is parallel to the letter E, that’s a pretty good start, the do the Lean find, or at 60% or below power, I just leave it there and it takes however long it takes to get whatever podunk airport I am going to.

While taxi, pull the knob until the upper lip of the mixture arm is parallel to to L, it is lean enough that I can’t even go to 1500 RPM or so without the engine quitting on me.

Last evening I couldn’t even get to proper LOP no matter how hard I tried, albeit I was low, at 3500 with OAT 14C. Anytime I pull below E Mark, the engine would complain. I believe I was right at peak at that point, or may be on the lean side a little. I just couldn’t get to a point where the EGT would start dropping, the engine would complain before that.

I will take that 6.4 gal per hour circling over lake for no reason any day. I didn’t buy an archer to go fast
 
26F336C7-1086-41B7-9758-FBE00E05510B.jpeg

Here is the article I believe is being referenced....I just opened up the latest AOPA issue this afternoon and saw it.

I can’t get my Lycoming IO-360’s CHTs anywhere near 350F though.
 
O360-A1A here in a Lancair 360. With the throttle wide open minus about 1/8" MP, I'm able to run it LOP. 1 of the cylinders is only about 10 LOP while the leanest is around 50-60 LOP. Does the job and keeps the CHTs reasonable.
 
jd21476 said:
I have been reading up a lot on LOP or ROP but I cant find which is best for my engine.
Click to expand...
You generally don't LOP in a carb'd engine. Without good tuned injectors into each cylinder you cannot guarantee the mixture going into each cylinder.. so you might have 1 cylinder at peak, 2 at ROP, 1 at LOP..

engine monitors have helped see the EGT of each cylinder so you can find peak.. but it's generally seen that carb'd = ROP

Granted.. at reduced power settings.. there's not much "damage" you can generally do.. so you'll hear stories about people who can fly "lop" when their at 8,5

PS.. thermodynamically there's no such thing as "best for the engine" - all the mixture setting and throttle plate do is regulate the "BOOM!" in the cylinder by adjusting how much air and how much fuel go into. You can cool that boom down by adding more fuel to it (ROP), or by adding more air to it (LOP). What you don't typically want to do is operate at peak BOOM! temp.. and with no mixture guarantee in a carb'd engine at the cylinder level you could end up running a carb'd engine with a portion of the cylinders at that no-go peak temp range
 
bobmrg said:
In an article about sticking valves in this month's AOPA Pilot magazine, Mike Busch disagrees with you. He says that sticking valves are caused by running too cool and recommends CHTs between 380 and 400 and aggressive leaning at low power settings.

Bob Gardner
Click to expand...

Wait what?
 
Jmcmanna said:
View attachment 86718

Here is the article I believe is being referenced....I just opened up the latest AOPA issue this afternoon and saw it.

I can’t get my Lycoming IO-360’s CHTs anywhere near 350F though.
Click to expand...

Maintaining 350 to 400 degrees F in a Lycoming is different than "running cool" enough to have issues with carbon or lead deposits and sticking valves. You'd need to be down in the mid 200s for that, which would be both low power and full rich mixture.

350-400 is also a lot different than 380-400.
 
idahoflier said:
Download this, it's a great reference! Read pages 3-6, 3-7 and 3-8, it tells you everything you need to know...

https://www.lycoming.com/content/operator's-manual-O-360-HO-360-IO-360-AIO-360-HIO-360-TIO-360-60297-12
Click to expand...

The graph is somewhat contradictory with the text. For example:

"1. LEANING TO EXHAUST GAS TEMPERATURE GAGE.
a. Normally aspirated engines with fuel injectors or uncompensated carburetors.
(1) Maximum Power Cruise (approximately 75% power) – Never lean beyond 150°F on rich side of peak EGT unless aircraft operator’s manual shows otherwise. Monitor cylinder head temperatures.
(2) Best Economy Cruise (approximately 75% power and below) – Operate at peak EGT."

However, the graph essentially disagrees with #2 as it shows best economy between -100 and 0 degrees lean of peak EGT. Given variation in EGT (about an 80 degree spread in my fuel injected engine), it makes more sense to lean toward the middle of that range (or at least as far as you can get toward the middle of the range and still have a smooth engine. If not, if you are watching the first cylinder to peak, you'll you'll have one cylinder at peak and the rest will be ROP and firmly in the red box. It only works if you monitor the last cylinder to lean, to ensure all the cylinders are lean of peak.

In fact, that's consistent with what they are recommending with #1 for max power cruise where they use the 150 degree ROP figure, which is firmly in the middle of the best power range. But again you'd need to consider what cylinder you are watching. If you are leaning from full rich, you want to be watching the leanest cylinder so it is at 150 ROP, and the rest are richer than that. If not, assuming an 80 degree spread, if you monitor the last cylinder to peak, it'll be at 150 ROP and the first to peak will be at 70 ROP - again in the red box.

In short, it's good information, but it is far short of everything you need to know.
 
idahoflier said:
Where do you see 75% power and below on the graph?
Click to expand...

"Best power" in the chart refers to a specific mixture for any given throttle setting. Percent of best power on the graph shows the change in percent power from that best power mixture. That curve is not showing 80% to 100% rated power of the engine.

For example, if you are flying a fixed pitch prop and set the throttle for 2400 rpm (around 60% power on my airplane), then start to lean from full rich, you'll see about a 5% increase in power as you reach the "best power" mixture at around 150 degrees ROP. On the tach you'll see a slight increase in RPM to around 2450-2475 rpm. As you lean further toward peak EGT, you'll see the RPM decrease back down to around 2400 RPM slightly lean of peak EGT. That's the top of best economy mixture range on the chart. If you keep leaning, it'll start to decrease significantly when you get farther on the lean side of peak. If you can get 100 degrees LOP and still have smooth engine operation you'll be generating only about 80% of your previous power at that throttle setting.

My fuel injected engine never stumbled when leaned excessively, it just lost several hundred RPM as I went way lean of peak. For example I might set the throttle for 2400, lean to peak RPM and continue leaning back to 2400. Then if I continued leaning the RPM would drop to around 2100 rpm before the bottom would fall out with significant power loss.

Prior to installing a JPI EDM-700, I'd start at my target cruse RPM at full rich, then start leaning through peak RPM, and then back down to my target RPM. That theoretically put me slightly LOP and in the nest economy range. Once I installed an EDM-700, I compared my old methods with LOP and ROP leaning using the EDM-700 and found the old methods were pretty much in the ballpark.
 
Larry Vrooman said:
"Best power" in the chart refers to a specific mixture for any given throttle setting. Percent of best power on the graph shows the change in percent power from that best power mixture. That curve is not showing 80% to 100% rated power of the engine.
Click to expand...

Agreed and I guess I should have been more verbose in my comment. I should have added that the while the chart provided is interesting information, Lycoming never said refer to that chart in their text for leaning instructions.

I was under the impression that below 75% power there wasn't much you could do to hurt the engine, however this discussion prompted me to read the various articles written by Mike Busch and John Deakin on the "Red Box" and "Red Fin" and I see now that's not necessarily true.
 
I too found the Mike Busch perspective from this month's AOPA Pilot magazine interesting. For those asking, the article is titled "Why Valves Stick" and is in the new July 2020 issue.

He says that he has recommended for a long time keeping CHTs no higher than 400F for continentals or 420F for lycomings, with "CHTs about 20F lower than those" being ideal. This was a new concept to me, and I've read everything Mike Busch has put out. He says in the AOPA article that some pilots think if a little CHT reduction is good, that lower is better, but that we should actually stay in a sweet spot between 350-400F. News to me, but hey, live and learn.

In my 177B Cardinal, which aren't known for their great cooling properties, it is pretty normal to see 400F peak on a hot day if you're climbing it hard. I've always gotten things down to about 330-340F when cruising, but sounds like maybe I need to run a bit warmer?
 
av8orDave said:
In my 177B Cardinal, which aren't known for their great cooling properties, it is pretty normal to see 400F peak on a hot day if you're climbing it hard. I've always gotten things down to about 330-340F when cruising, but sounds like maybe I need to run a bit warmer?
Click to expand...

I don’t know about that. I can’t get my Arrow’s CHTs above about 330 no matter how hard I try...25 LOP (60%) my hottest CHT is at 300 or less. I suspect he had bigger engines in mind, maybe....but a lean mixture and low CHTs has always been Mike Busch’s main objectives.
 
Jmcmanna said:
I don’t know about that. I can’t get my Arrow’s CHTs above about 330 no matter how hard I try...25 LOP (60%) my hottest CHT is at 300 or less. I suspect he had bigger engines in mind, maybe....but a lean mixture and low CHTs has always been Mike Busch’s main objectives.
Click to expand...

My Commander is the same. The IO360 C1D6 never runs above 340. In cruise I run 22/2450, it's smooth, quiet, and seems to run happy there all day.
 
You must log in or register to reply here.
Back
Top